Trying to purchase Alhambra tickets for mid September, 2018 (within 90 day arrival period) with American Master Card on the official Alhambra web site. I had assumed this problem was resolved since all Trip Advisor posts on this issue went silent by end of November, 2017.
Try a VISA. All my transactions with a MC in Spain were problematic.
Gary,
Make sure you call your credit card company to notify them of this foreign transaction prior to booking your tickets.
If all else fails, you can order by phone directly from the Alhambra.
The Alhambra website also provides an online “chat” where you can ask your questions. This information is found at the very bottom of the Alhambra website.
Hope this helps!
Edited to add...
BTW, you can pay for Alhambra tickets online with Visa or MasterCard